Tomographic reconstruction of heat release rate perturbations induced by helical modes in turbulent swirl flames
- 594 Downloads
Swirl flows with vortex breakdown are widely used in industrial combustion systems for flame stabilization. This type of flow is known to sustain a hydrodynamic instability with a rotating helical structure, one common manifestation of it being the precessing vortex core. The role of this unsteady flow mode in combustion is not well understood, and its interaction with combustion instabilities and flame stabilization remains unclear. It is therefore important to assess the structure of the perturbation in the flame that is induced by this helical mode. Based on principles of tomographic reconstruction, a method is presented to determine the 3-D distribution of the heat release rate perturbation associated with the helical mode. Since this flow instability is rotating, a phase-resolved sequence of projection images of light emitted from the flame is identical to the Radon transform of the light intensity distribution in the combustor volume and thus can be used for tomographic reconstruction. This is achieved with one stationary camera only, a vast reduction in experimental and hardware requirements compared to a multi-camera setup or camera repositioning, which is typically required for tomographic reconstruction. Different approaches to extract the coherent part of the oscillation from the images are discussed. Two novel tomographic reconstruction algorithms specifically tailored to the structure of the heat release rate perturbations related to the helical mode are derived. The reconstruction techniques are first applied to an artificial field to illustrate the accuracy. High-speed imaging data acquired in a turbulent swirl-stabilized combustor setup with strong helical mode oscillations are then used to reconstruct the 3-D structure of the associated perturbation in the flame.
KeywordsRadon Proper Orthogonal Decomposition Heat Release Rate Proper Orthogonal Decomposition Mode Tomographic Reconstruction
This work is supported by the Agence Nationale de la Recherche, contract N° ANR-08-BLAN-0027-01, the Délégation Générale pour l’Armement, and by Snecma (Safran Group).
- Abramowitz M, Stegun IA (1964) Handbook of mathematical functions with formulas, graphs, and mathematical tables, 9th edn. Dover, New YorkGoogle Scholar
- Gupta AK, Lilley DG, Syred N (1984) Swirl flows. Abacus Press, Tunbridge WellsGoogle Scholar
- Lefebvre A (1998) Gas Turbine Combustion, 2nd edn. Taylor and Francis, LondonGoogle Scholar
- O’Connor J, Lieuwen T (2012) Recirculation zone dynamics of a transversely excited swirl flow and flame. Phys Fluids 24:075107 (30 pp)Google Scholar
- Palies P, Schuller T, Durox D, Gicquel L, Candel S (2011) Acoustically perturbed turbulent premixed swirling flames. Phys Fluids 23:037101 (15 pp)Google Scholar
- Schimek S, Moeck JP, Paschereit CO (2011) An experimental investigation of the nonlinear response of an atmospheric swirl-stabilized premixed flame. J Eng Gas Turbines Power 133:101502 (7 pp)Google Scholar
- Worth NA, Dawson JR (2013) Tomographic reconstruction of OH* chemiluminescence in two interacting turbulent flames. Meas Sci Technol 24:024013 (11 pp)Google Scholar